Fig. 25.8 (a) Color photograph OS from a patient with thrombotic thrombocytopenic purpura (TTP). The patient experienced severe bilateral loss of vision secondary to

Fig. 25.9 (a) Color photograph OD depicting findings from a patient with amniotic fluid embolization. Multiple cotton-wool spots are noted, along with areas of retinal

occlusive vasculopathy. (b) The FA shows virtually complete shutdown of blood flow

ischemia. (b) The FA confirms a moderate degree of capillary non-perfusion

detachments, and optic disk neovascularization [31–34] (Fig. 25.8a, b). A Purtscher’s-like retinopathy has also been reported with TTP [35].

Amniotic Fluid Embolism

Amniotic fluid embolism is a serious complication of pregnancy, with an 80% mortality rate. It occurs during labor, delivery, or in the immediate postpartum period. Particulate matter from the amniotic fluid enters the maternal circulation, causing cardiopulmonary failure. Ophthalmic manifestations include retinal artery occlusions [36] and capillary non-perfusion (Fig. 25.9a, b).

Preexisting Conditions

Diabetic Retinopathy

Progression

Pregnancy is a major risk factor for the progression of diabetic retinopathy, as has been reported by Klein and associates [37]. Several studies have outlined the degree of the retinopathy progression during the course of pregnancy [1, 37–40]. Axer-Seigel and coworkers examined 65 patients with insulin-dependent diabetes mellitus who became pregnant [37]. They reported that 26% of

patients without diabetic retinopathy at conception developed mild non-proliferative diabetic retinopathy (NPDR) during the course of pregnancy. Fifty-five percent of patients with initial NPDR had progression of their non-proliferative retinopathy, while 22.5% of patients with initial NPDR progressed to proliferative diabetic retinopathy (PDR) necessitating the need for panretinal photocoagulation.

Both NPDR and PDR occurring during the course of pregnancy have a high rate of spontaneous regression in the third trimester or in the postpartum period. As reported by Axer-Seigel [37], of the patients with no retinopathy at conception who then developed mild NPDR during pregnancy, 50% experienced total regression of their retinopathy and 30% had partial regression of their retinopathy after delivery. The rate of total regression was not as high in patients with more advanced disease at the onset of pregnancy. Total regression was noted in only 17% of patients with NPDR initially who progressed to severe NPDR during pregnancy.

Diabetic macular edema may also occur during pregnancy [41, 42], and as noted with other forms of retinopathy, there is a high rate of spontaneous regression postpartum.

Factors Associated with Progression

The progression of diabetic retinopathy is influenced by various factors, including the duration of diabetes mellitus, metabolic control before and during pregnancy, severity of retinopathy at conception, and the presence of coexisting hypertension. Diabetic retinopathy progression is more likely to occur in pregnant women who have had diabetes for a longer period of time, as is also the case for nonpregnant diabetics [38].

Several studies have also shown that both higher glycosylated hemoglobin levels at conception and rapid tightening of glycemic control during pregnancy have been associated with a higher risk of progression of retinopathy [39, 43]. In contrast, Axer-Seigel and associates found no association between the retinopathy status and the levels of glycosylated hemoglobin at conception or with the institution of tighter metabolic control during the pregnancy [38]. They did note

that the glycosylated hemoglobin levels were higher in patients who had progression of their retinopathy as compared to those who did not have progression, but this difference was statistically significant only in the third trimester. Lauszus and coworkers found no association between the progression of retinopathy and the glycosylated hemoglobin [44].

Another factor that influences the progression of diabetic retinopathy during pregnancy is the degree of retinopathy at conception. Those patients with preexisting diabetic retinopathy are at a high risk of progression of their disease during pregnancy [1, 38, 45]. Progression to proliferative retinopathy without the initial presence of non-proliferative retinopathy in early pregnancy is rare but has been reported in three pregnant diabetic patients who were treated with a specific type of insulin, insulin lispro [46].

Finally, both high diastolic and systolic blood pressure have been reported to be associated independently with diabetic retinopathy progression [37, 38].

Pathophysiology of Progression

The pathogenesis for the acceleration of diabetic retinopathy during pregnancy is unclear. Several investigators have studied retinal circulatory changes in diabetic and control subjects during pregnancy. Chen and associates found an increase in retinal blood flow in pregnant women who had worsening of their diabetic retinopathy [47]. In contrast, Schocket and coworkers noted that the retinal venous diameter and retinal blood flow decreased to a greater degree in diabetic mothers compared to nondiabetic mothers [48]. Thus, they proposed that the decrease in blood flow might exacerbate retinal ischemia and hypoxia, leading to the acceleration of diabetic retinopathy.

Treatment Criteria for Diabetic Retinopathy

The treatment of proliferative diabetic retinopathy during pregnancy is based on the same criteria, as defined by the Diabetic Retinopathy Study, as in nonpregnant patients [49]. Diabetic macular edema is often observed without treatment due to